JPS6161922B2 - - Google Patents

Description

Claim 1: A backing plate having at least one sheet attached to one side of a core member, the core member opening to form a groove extending long from one end of the sheet to the other end. , placing a backing board under the printed circuit board, drilling holes through the sheet of the printed circuit board and backing board, and stopping the drilling at a portion of the core member after drilling through the sheet. Method.

2. The method according to claim 1, wherein the core member is sandwiched between the pair of sheets.

3. The method according to claim 1 or 2, wherein both the sheet and the core member are made of metal materials.

4. A method according to any one of claims 1 to 3, characterized in that the core member has an undulating shape with grooves running substantially parallel to each other.

5. The method of claim 4, wherein the wave shape is substantially sinusoidal.

6 The thickness of the material of the sheet and core member is approximately
6. The method of claim 1, wherein the thickness of the backing plate is approximately 0.063 inches.

7. The method according to any one of claims 1 to 6, characterized in that air is sent through the grooves of the core member in order to cool the printed circuit board and the drill and to remove chips produced by drilling. Method.

Description This invention relates to drilling printed circuit boards, and more particularly, to a method of drilling printed circuit boards using a backing board. to provide the necessary holes for passage of the component introduction and proper attachment to the plate.
When drilling printed circuit boards, a problem has been encountered in which burr develops from the copper-coated surface on the periphery of the hole where the drill resides.
Such burrs are unacceptable because they can bulge between the through-hole platings, trap dirt and air, and later cause cracks in the through-hole plating. Such blisters must therefore be removed by another sanding operation or prevented by the use of suitable backing plates. The latter method is much more desirable than the former because it is less expensive and does not increase the time required for polishing.

A particularly desirable backing plate for use in drilling holes in circuit boards is described in U.S. Pat. has been done. This prior art backing plate is a metal foil (preferably aluminum)
It uses a highly compressed wood core covered with an outer layer of. The backing plate of the prior patent mentioned above is very effective in removing bulges and can cool the drill to some extent, but the presence of chips during drilling makes it difficult to perform accurate drilling. Furthermore, the cooling of the drill was not sufficient.

The object of the present invention is to provide a novel method for drilling printed circuit boards, which improves on such conventional methods and allows very effective removal of chips and also significantly accelerates cooling of the workpiece and drill. With the goal.

The method of the present invention provides a backing plate having at least one sheet attached to one side of a core member, the core member forming and opening a groove extending long from one end of the sheet to the other. placing a backing board under the printed circuit board, drilling holes through the sheet of the printed circuit board and backing board, and stopping the drilling at the core member after drilling through the sheet. .

That is, in the present invention, the presence of open spaces in the core member of the backing plate allows air to flow through the spaces or grooves during drilling to facilitate cooling of the drill and printed circuit board workpiece. Further, since chips generated during drilling can be removed from the opening of the core member, the workability and accuracy of drilling can be improved. Furthermore, the tip of the drill
After passing through the sheet, the drill enters the core member, which has the above-mentioned effects, and stops drilling there, so that the cooling of the drill is carried out more effectively.

Note that the method of the present invention has the advantage that a vacuum device can be used for removing chips and cooling the drill and the like.

Next, embodiments of the present invention will be described with reference to the accompanying drawings.

1 is a perspective view of the backing material of the present invention; FIG. 2 is a cross-sectional view taken along the plane 2--2 of FIG. 1; and FIG. , a cross-sectional view taken along the plane shown at 3-3 in FIG. Figure 5 is a schematic diagram illustrating the production of the backing material of the invention.

Briefly, the backing plate consists of a pair of opposed metal foils made of copper, magnesium, or steel, but preferably aluminum, with a core having opposed nodes between them. The members are sandwiched, one facing toward one of such sheets and the other facing toward the other of the sheets. The knots preferably run substantially parallel to each other between the ends of the sheet, and may have a nearly sinusoidal shape. The circuit board to be drilled is placed on the backing material with its lower surface adjacent to the upper surface of the backing material. The drill passes through the workpiece,
After driving, it is driven into the top sheet of backing material and enters the core space, but does not advance beyond this space. in the core to facilitate the removal of chips emerging therefrom and to aid in the cooling of the drill and workpiece.
You can create air flow.

1-3, preferred embodiments of the backing material of the present invention are depicted. The material includes an upper metal foil sheet 11 and a lower metal foil sheet 12, between which a corrugated core member 14 is sandwiched. Core member 14
has opposed knurls 14a and 14b facing the inner surfaces of sheets 11 and 12, respectively. Knot 1
4a and 14b using a suitable adhesive substance 13,
It is glued to sheets 11 and 12 and runs between the ends of the sheets, each of these nodes running adjacent and almost parallel to the sheets. Aluminum foil has been found to be particularly suitable for sheets 11 and 12 and core 14.

For each of these components, the thickness
Excellent results were obtained using 0.013 cm (0.005 inch) 3003H19 type aluminum foil.
This type of aluminum adds the following ingredients to pure aluminum: Silicon 6%, Iron 7%, Copper 0.05
-0.20%, manganese 1.0-1.5% and zinc 0.10
%. Displayed as 0.013cm (0.005 inch) thick,
With this type of aluminum, the spacing between the inner walls of the two foils is typically about 0.13 cm (approx.
The total thickness of the backing material should be 0.16 cm (0.063 inch). Total thickness is 0.24
cm (0.093 inch) of backing material typically includes top and bottom sheets and a core.
It has a thickness of 0.018 cm (0.007 inch), with a total thickness of
The 0.32 cm (0.125 inch) backing material typically includes top and bottom sheets and a core material.
It has a thickness of 0.023 cm (0.009 inch).

Referring to FIG. 4, the operation of the present invention is schematically illustrated. Typically, both sides are covered with copper layers 20
Epoxy glass substrate 20 coated with b and 20c
The workpiece 20 is a printed circuit board using a.
A piece of backing material 15 is placed on top. As indicated by arrow 21, a supply of air is applied to a portion of the spiral core material 14. This supplied air flows through the drill hole 22 and air outlet 2
Exit through 3. The air supply may be provided by a blower or a suitable vacuum device, the latter being present in a typical drilling machine. The drill 25 is set such that the drill bit 29, at its deepest point, does not penetrate more than 14 parts of the core material, eg, into the lower sheet 12 of backing material. This allows the backing material to move towards the drill after it has been used on one side.
By placing the reverse, unused side, the backing material can be used twice. During the drilling operation (once driving of the workpiece 20 has occurred) air flows through the groove of the drill bit and
The tip of the drill is cooled. Air circulates through the core material and also facilitates cooling of the drill bit and workpiece. Immediately after the drill bit is withdrawn, air flows through the drill hole 22 to remove any chips left in the vicinity.

The device shown in FIG. 4 has a pressure leg 28 that quickly moves downward and contacts the plate 20 before making the hole. This action ensures that the plate is flat and ensures initial contact when drilling. When the drill reaches the desired predetermined maximum depth, which does not exceed the core as already indicated, the downward movement of the drill automatically stops and the upward movement begins. The stop position between the downward and upward movements, known as the "dwell", is, in prior art drills, when the drill always reaches its highest temperature. When the drill is completely withdrawn, a vacuum is created at the air outlet 23, which is used to remove debris from the top of the workpiece. An air supply 21 provided in the core of the lining material is used for the cooling process;
It aids in the removal of debris and is particularly effective at this last point, debris below and within the hole. Thus, the use of a backing material in accordance with the present invention greatly facilitates cooling of the workpiece and drill and removal of chips and other debris.

Referring to FIG. 5, a method of manufacturing the backing material used in the present invention is illustrated. First and second rolls 33 and 34 of aluminum foil
is rotatably supported and fed in unwinding relation to a pinch roll 36, by which it is unwound. pinch roll 36
Before reaching the surface of the foil sheets 11 and 12, the outer surfaces of the sheets are coated with a layer of adhesive substance 13. It passes through rolls 38 and 39. It has been found that an epoxy resin adhesive containing a 50-50 composition of epoxy and hardener is a suitable adhesive. Similarly, the corrugated core material 14 is sandwiched between sheets 11 and 12 through pinch rolls. The corrugations of core material 14 can be formed into a flat sheet of foil using a suitable pair of forming rolls. Typically, the nodes run nearly parallel to each other along the length of the core.
Waves are formed. Typically, 0.06cm (0.002
A layer of adhesive material 13 (inches) is applied to each metal foil sheet. The core material sandwiched between
After passing through the pinch rolls 36, the final bond is applied at a pressure of 1.8 to 22.8 Kg/cm ² (25 to 325 psi) (in a preferred embodiment, 3.5 Kg/cm ² to 50 psi has been found to be suitable). ), temperature 52-288℃ (125-
550〓) (in a preferred embodiment, 116℃−240〓−
is found to be suitable) and the final result of this is shown above by placing the material between a pair of machining or "curling" tables and then placing it in a heated laminating press. This is achieved by applying heat and pressure.

Having described and explained the invention in detail, it is
It should be expressly understood that it is intended for purposes of illustration and example only, and should not be considered limiting. The spirit and scope of the invention is limited only by the following claims.